Method of manufacturing a semiconductor device

ABSTRACT

In a lead frame, through holes are formed outside suspending leads and trenches are formed on a back surface along the suspending leads so as to communicate with the through holes. When sealing resin is injected into cavities of a resin molding die, air enters the through holes through air vents and flows out from the through holes by a resin injection pressure in the trenches, making it easier for the sealing resin to enter the through holes. Since the sealing resin leaking to the air vents can be injected into the through holes, it is possible to enhance the bonding force between the sealing resin after curing and the lead frame in the vicinity of the air vents and effect release of the resin molding die, while allowing the sealing resin leaking to the air vents to remain on the lead frame side without remaining within the air vents.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese patent applicationNo. 2004-135259, filed on Apr. 30, 2004, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates in general to a method of manufacturing asemiconductor device and a lead frame. Particularly, the presentinvention is concerned with a technique which is effective fordecreasing the cleaning frequency of a resin molding die.

According to a conventional method of manufacturing a semiconductordevice, a matrix lead frame is provided, which has a plurality of unitlead frame patterns arranged longitudinally and transversely in alattice shape; then, semiconductor chips are fixed and electrodes of thesemiconductor chips and inner ends of leads are connected together usingwires; and, thereafter, the semiconductor chips, wires and lead innerends are covered with a sealing body (package) by one-side molding. Inthis case, a contact preventing member that is thicker than the packageis formed outside the package with the use of injected resin (see, forexample, Patent Literature 1).

[Patent Literature]

Japanese Unexamined Patent Publication No.

2002-151625 (FIG. 1)

SUMMARY OF THE INVENTION

In a non-leaded semiconductor device, such as a QFN (Quad FlatNon-leaded Package), leads are partially exposed to the outer edgeportions on a back surface, thereby serving as external terminals.

Therefore, in a resin sealing process as used in assembling such a QFN,a sealing sheet is disposed on one die surface (e.g., a surface of alower die) of a resin molding die in such a manner that the leads aresure to be exposed to a back surface of a sealing body; and, then, alead frame is disposed on the sealing sheet, and resin molding isperformed in a state in which the leads are in close contact with thesealing sheet, whereby the leads are exposed to the back surface of thesealing body, while preventing the sealing resin from adhering to a partof each lead.

According to such a resin sealing method, at the time of forming airvents in the resin molding die, since the sealing sheet is disposed onone die surface, the air vents can be formed on only the other diesurface on which the sealing sheet is not disposed.

In the lead frame, through holes are formed outside suspending leads andin positions corresponding to the air vents of the resin molding die,and the sealing resin leaking to the air vents is allowed to enter thethrough holes and harden, whereby, at the time of mold release, thesealing resin present within the air vents is allowed to remain on thelead frame side, lest the sealing resin should remain within the airvents of the resin molding die.

In resin sealing for a QFN, when sealing resin is injected into a cavityof the resin molding die, the air present within the cavity flowsthrough the air vents into the through holes formed outside thesuspending leads. However, since one of the openings of the throughholes is closed by the sealing sheet, the air stays within the throughholes, and, hence, a phenomenon occurs in which the sealing resinleaking into the air vents does not enter the through holes orside-steps the through holes.

As a result, after mold release, the sealing resin remains on the dieside, causing clogging of the air vents or incomplete filling of resin.

Moreover, since the sealing resin remains on the die side, the cleaningfrequency for the resin molding die increases, thus giving rise to theproblem that the throughput in the resin sealing process in assembling aQFN becomes lower.

It also has been proposed to use a method wherein resin sealing isperformed without using the sealing sheet in assembling a QFN. In thiscase, however, since the sealing resin adheres to the surface to beexposed of each lead, a process for removing the sealing resin that hasadhered to each lead on the back surface of the sealing body is neededafter the resin sealing process, thus causing the problem that theproductivity in assembling a QFN is deteriorated.

In paragraph [0068] of the foregoing Patent Literature 1, it isindicated that resin cured in air vents is allowed to bite into holesformed in a lead frame to prevent the cured resin in the air vents fromfalling off. In the resin sealing process which adopts the use of asealing sheet for a QFN, air stays within the holes and the sealingresin does not enter the holes, so that it is presumed to be impossibleto prevent fall-off of the resin that has cured in the air vents.

It is an object of the present invention to provide a method ofmanufacturing a semiconductor device which can reduce the cleaningfrequency for a resin molding die, as well as a lead frame used for themethod.

It is another object of the present invention to provide a method ofmanufacturing a semiconductor device which can improve the throughput ofassembly, as well as a lead frame used for the method.

It is a further object of the present invention to provide a method ofmanufacturing a semiconductor device which can improve the quality of aproduct, as well as a lead frame used for the method.

The above and other objects and novel features of the present inventionwill become apparent from the following description and the accompanyingdrawings.

Typical modes of the present invention as disclosed herein will beoutlined below.

In one aspect of the present invention, there is a method ofmanufacturing a semiconductor device, which has a lead frame, the leadframe having chip mounting portions, suspending leads connected to eachof the chip mounting portions, a plurality of leads arranged around eachof the chip mounting portions, through holes formed outside thesuspending leads in extending directions of the suspending leads, andtrenches formed along the suspending leads on a back surface sideopposite to the chip mounting portion side so as to communicate with thethrough holes; the method comprising the steps of mounting semiconductorchips respectively onto the chip mounting portions; connectingelectrodes of the semiconductor chips and the leads with each otherthrough electrically conductive wires; disposing the lead frame onto adie surface of a resin molding die, thereafter aligning the air ventsformed in the resin molding die and the through holes and trenchesformed in the lead frame so as to correspond to each other, clamping theresin molding die, then injecting sealing resin into cavities of theresin molding die, allowing air which has entered the through holesthrough the air vents and the trenches to flow out from the throughholes by virtue of an influent pressure of the sealing resin, andperforming resin sealing so that the sealing resin is injected into thecavities and the through holes; after the resin sealing, allowing thesealing resin to remain in the through holes of the lead frame withoutallowing it to remain in the air vents, and releasing the resin moldingdie; and separating the leads and the suspending leads from the leadframe to divide the lead frame into individual chip mounting portions.

In another aspect of the present invention, there is a method ofmanufacturing a semiconductor device, which has a lead frame, the leadframe having a plurality of device regions, the device regions eachhaving a chip mounting portion, suspending leads connected to the chipmounting portion, and a plurality of leads arranged around the chipmounting portion, the lead frame further having through holes formedoutside the suspending leads in extending directions of the suspendingleads, the through holes each disposed in an elongated shape along anextending direction of a gate runner in an adjacent device region when aresin molding die is clamped; the method comprising the steps ofmounting semiconductor chips respectively onto the chip mountingportions; connecting electrodes of the semiconductor chips and the leadswith each other through electrically conductive wires; disposing thelead frame onto a die surface of the resin molding die, thereafteraligning the air vents formed in the resin molding die and the throughholes formed in the lead frame so as to correspond to each other,clamping the resin molding die, then injecting sealing resin intocavities of the resin molding die through respective gate runners,allowing air present within the through holes to flow out from thethrough holes by virtue of an influent pressure of the sealing resin,and performing resin sealing so that the sealing resin is filled intothe cavities and the through holes; after the resin sealing, allowingthe sealing resin to remain in the through holes of the lead frame andreleasing the resin molding die; and separating the leads and thesuspending leads from the lead frame to divide the lead frame intoindividual device regions.

In a further aspect of the present invention, there is a lead framecomprising chip mounting portions capable of mounting semiconductorchips respectively thereon, suspending leads connected to each of thechip mounting portions, a plurality of leads arranged around each of thechip mounting portions, and frame portions connected to the suspendingleads and the leads, the frame portions having through holes formedoutside the suspending leads in extending directions of the suspendingleads and trenches formed so as to communicate with the through holesalong the suspending leads on a back surface side opposite to the chipmounting portion side.

The following is a brief description of effects obtained by typicalmodes of the present invention as disclosed herein.

Since through holes are formed outside the suspending leads in the leadframe and trenches are formed on the back surface side so as tocommunicate with the through holes along the suspending leads, air whichhas entered the through holes through the air vents and the trenches canbe allowed to flow out from the through holes by virtue of an influentpressure at the time of injection of sealing resin into the cavities. Asa result, the sealing resin can be filled into the through holes.Consequently, it is possible to enhance the bonding force between thesealing resin after curing and the lead frame in the vicinity of the airvents, and, at the time of release of the resin molding die, it ispossible to release the die while allowing the sealing resin presentwithin the air vents to remain on the lead frame side. Thus, it ispossible to prevent clogging of the air vents in the resin molding dieand, thereby, to decrease the cleaning frequency for the die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an example of the structure of asemiconductor device assembled by a semiconductor device manufacturingmethod according to an embodiment of the present invention;

FIG. 2 is a side view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a structural sectional view taken along the line A—A in FIG.3;

FIG. 5 is a manufacturing flowchart showing an example of the procedureused for assembling the semiconductor device illustrated in FIG. 1;

FIG. 6 is a plan view showing an example of the structure of a leadframe used in assembling the semiconductor device illustrated in FIG. 1;

FIG. 7 is an enlarged plan view showing an example of the structure of acorner portion of a device region in the lead frame of FIG. 6;

FIG. 8 is a sectional view taken along the line A—A in FIG. 7;

FIG. 9 is a sectional view taken along the line B—B in FIG. 7;

FIG. 10 is a perspective view showing an example of the structure of adie corner portion in a state in which a die is clamped in a resinsealing process during assembly of the semiconductor device illustratedin FIG. 1;

FIG. 11 is an enlarged sectional view showing the structure of the diecorner portion in the die clamping illustrated in FIG. 10;

FIG. 12 is a sectional view showing an example of the resin flow in astate in which resin is injected in the resin sealing process duringassembly of the semiconductor device illustrated in FIG. 1;

FIG. 13 is a sectional view taken along the line A—A in FIG. 7, showingthe structure after resin fill;

FIG. 14 is a sectional view taken along the line B—B in FIG. 7, showingthe structure after resin fill;

FIG. 15 is an enlarged plan view showing the structure of a cornerportion of a device region in a lead frame according to a modificationof the embodiment;

FIG. 16 is an enlarged plan view showing an example of a layoutrelationship between a through hole and an adjacent gate runner in thelead frame of the modification illustrated in FIG. 15;

FIG. 17 is an enlarged plan view showing the structure of a cornerportion of a device region in a lead frame according to anothermodification of the embodiment; and

FIG. 18 is an enlarged plan view showing the structure of a cornerportion of a device region in a lead frame according to a furthermodification of the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of the embodiments, as to the same orsimilar portions, repeated explanations thereof will be omitted inprinciple except where required.

Where required for convenience's sake, the subject matter of the presentinvention will be described in a divided manner as plural sections orembodiments, but unless otherwise mentioned, they are not unrelated toeach other, but are in a relation such that one is a modification, adetailed description or a supplementary explanation of part or the wholeof the other.

In the following description of the embodiments, when reference is madeto a number of elements (including the number, numerical value,quantity, and range), no limitation is made to the number referred to,but numerals above and below the number referred to will do as well,unless otherwise mentioned and except for the case where it is basicallyevident that a limitation is made to the number referred to.

The embodiments of the present invention will be described in detailhereinunder with reference to the accompanying drawings. In all of thedrawings, constituent members having the same functions are identifiedby the same reference numerals, and repeated explanations thereof willbe omitted in the following description.

Embodiments

A semiconductor device according to an embodiment of the presentinvention, as illustrated in FIGS. 1 to 4, is a small-sized non-leadedtype device, wherein plural leads 1 a are arranged side by side on outeredge portions of a back surface 3 a of a sealing body 3 in such a mannerthat each of the leads 1 a is partially exposed. In the description ofthis embodiment, reference will be made below to a QFN 5 as an exampleof the semiconductor device.

A description will now be given as to the construction of the QFN 5. Asshown in FIG. 4, the QFN 5 comprises a semiconductor chip 2 having, on amain surface 2 b thereof, a semiconductor element and plural pads(electrodes) 2 a; a tab 1 b serving as a chip mounting portion connectedto the semiconductor chip 2; bus bars 1 i which are disposed outside thesemiconductor chip 2 and are connected to the tab 1 b through connectingportions 1 k, as shown in FIG. 3; a sealing body 3 which seals thesemiconductor chip 2 with resin; plural leads 1 a which are arrangedaround the semiconductor chip 2 so that respective to-be-connectedsurfaces (portions) 1 g are exposed at outer edge portions of a backsurface 3 a of the sealing body 3, suspending leads 1 e which arearranged respectively at positions corresponding to the four corners ofthe sealing body 3 and are connected to the tab 1 b; plural first wires4 a which connect the plural pads 2 a of the semiconductor chip 2 andcorresponding plural leads 1 a with each other, as shown in FIG. 4; andplural second wires 4 b which connect predetermined pads 2 a of thesemiconductor chip 2 and the bus bars 1 i with each other.

In the QFN 5 of this embodiment, the bus bars 1 i are arranged aroundthe semiconductor chip 2, and predetermined plural pads 2 a, such asground (GND) or power-supply pads 2 a, are connected to the bus bars 1 ithrough the second wires 4 b by down bonding. In this way, the leads 1 aare used in common to reduce the number of input/output pins and therebyattain a further reduction of the size of the device.

The bus bars 1 i are arranged around the tab 1 b as a chip mountingportion through a gap, and both ends thereof are connected to thesuspending leads 1 e. The bus bars 1 i are arranged outside thesemiconductor chip 2 so that they can be wire-bonded to thesemiconductor chip.

Not only the to-be-connected surfaces 1 g of the leads 1 a, but also aback surface 1 d of the tab 1 b, back surfaces 1 j of the bus bars 1 iand back surfaces 1 f of the suspending leads 1 e are each partiallyexposed to the back surface 3 a of the sealing body 3.

It is preferable that the pads 2 a of the semiconductor chip 2, whichare connected to the bus bars 1 i through the second wires 4 b, beground or power-supply electrodes capable of serving as common pins. Forexample, when a bus bar 1 i is connected to a ground pad 2 a, a groundpotential is applied to the bus bar 1 i.

As shown in FIG. 4, the semiconductor chip 2 is fixed onto a mainsurface 1 c of the tab 1 b with use of, for example, a die bondingmaterial (e.g., silver paste) 6, whereby a back surface 2 c of thesemiconductor chip 2 and the main surface 1 c of the tab 1 b areconnected together through the die bonding material 6.

Plural leads 1 a, which are arranged side by side on the outer edgeportions of the back surface 3 a of the sealing body 3 in the QFN 5, arerespectively exposed partially as to-be-connected surfaces 1 g on theback surface 3 a of the sealing body 3. The to-be-connected surfaces 1 gare exteriorly plated with solder or palladium.

The tab 1 b, suspending leads 1 e and leads 1 a are formed using acopper alloy sheet, for example. The first wires 4 a for connecting pads2 a of the semiconductor chip 2 and corresponding leads 1 a, as well asthe second wires 4 b for connecting ground pads 2 a of the semiconductorchip 2 and bus bars 1 i, are gold wires, for example. The sealing body 3is formed by resin sealing in accordance with a molding method. Thesealing resin used in this molding method is, for example, athermosetting epoxy resin.

Next, the method of manufacturing the QFN 5 (semiconductor device) ofthis embodiment will be described below with reference to themanufacturing process flowchart of FIG. 5.

First, a lead frame 1, as shown in FIG. 6, is provided in step S1. Thelead frame 1 includes a tab 1 b capable of carrying the semiconductorchip 2 thereon, suspending leads 1 e connected to the tab 1 b, pluralleads 1 a arranged around the tab 1 b, and bus bars 1 i connected to thetab 1 b through connecting portions 1 k and arranged outside the tab 1b. As shown in FIG. 7, the lead frame 1, which is shown in its entiretyin FIG. 6, further includes through holes 1 n formed outside thesuspending leads 1 e in the directions of extension of the suspendingleads 1 e, and trenches 1 h (first trenches) are formed on a backsurface side opposite to the chip mounting side so as to communicatewith the through holes 1 n along the leads 1 e.

More specifically, in each of the device regions 1 m formed on the leadframe 1, a circular through hole 1 n is formed in an outer frame portion1 p at a position outside each suspending lead 1 e and in the directionof extension of the suspending lead, as shown in FIG. 7. Further, on aback surface side opposite to the chip mounting side of the frameportion 1 p, trenches 1 h, as shown in FIGS. 8 and 9, are formed alongand on both sides of the suspending lead 1 e so as to communicate withthe through hole 1 n from the suspending lead side.

When sealing resin 7 is injected into a cavity 9 c of a resin moldingdie 9 in a resin sealing process, as shown in FIGS. 12 and 13, thesealing resin passing through an air vent 9 e is allowed to get into thethrough hole 1 n and is cured therein, and then the sealing resin 7remaining within the air vent 9 e is allowed to adhere to and remain onthe lead frame 1 side at the time of releasing the die, leaving littleresin within the air vent 9 e. The through hole 1 n functions in thisway. That is, the through hole 1 n serves as a resin trap for allowingthe sealing resin 7 remaining within the air vent 9 e to adhere to thelead frame 1 side at the time of die release.

Therefore, the through hole 1 n is formed so as to be located outsidethe cavity 9 c and at a position corresponding to the air vent 9 e whenclamping the resin mold die 9.

Each trench 1 h serves as an air flow outlet path for causing air whichhas entered the through hole 1 n through the air vent 9 e and trench 1 hwith influent pressure of the sealing resin 7 to flow out of the throughhole 1 n.

In the lead frame 1 thus constructed, at the time of injecting resininto the cavity 9 c, a portion of the air extruded by an injectionpressure at first gets into the through hole 1 n; and, thereafter, sinceresin is injected also from the trench 1 h, the air is extruded to theexterior of the through hole 1 n by an injection pressure exertedthereon from the trench 1 h side. As a result, air does not stay withinthe through hole 1 n, and, therefore, it is possible to facilitate entryof the sealing resin 7 into the through hole 1 n.

For example, the trench 1 h is formed by half etching or stamping.

As shown in FIG. 6, the lead frame 1 is a strip-like frame member onwhich plural device regions 1 m are formed continuously, each of thedevice regions 1 m comprising a tab 1 b, plural leads 1 a arrangedaround the tab 1 b, suspending leads 1 e connected to the tab 1 b, busbars 1 i connected to the tab 1 b through connecting portions 1 k, andframe portions 1 p which surround those components. For example, thelead frame 1 is formed of a copper alloy.

In the QFN 5, in the case where the exterior of the to-be-connectedsurface 1 g of each lead 1 a is plated with palladium, the lead frame 1is plated beforehand with palladium throughout the whole surfacethereof.

Thereafter, die bonding is performed in step S2 shown in FIG. 5. In thisstep, a semiconductor chip 2 is fixed onto the main surface 1 c of eachtab 1 b, which serves as a chip mounting portion on the lead frame 1,through a die bonding material 6, for example.

Subsequently, wire bonding is performed in step S3. In this step, asshown in FIG. 4, pads 2 a on the semiconductor chip 2 and correspondingleads 1 a are connected together through electrically conductive firstwires 4 a, such as gold wires. Further, pads 2 a for ground (or forpower supply) on the semiconductor chip 2 and bus bars 1 i are connectedtogether through electrically conductive second wires 4 b, such as goldwires.

Then, resin sealing (resin molding) is performed in step S4. Accordingto a resin sealing method adopted in this embodiment, the individualdevice regions 1 m of the lead frame 1 are covered respectively withcavities 9 c of an upper die 9 a of the resin molding die 9, and thesealing resin 7 is injected into the cavities 9 c.

First, as shown in FIG. 12, the lead frame 1 is disposed onto a diesurface 9 d of a lower die 9 b of the resin molding die 9 so as to beplaced on a film sheet 8, which is a sealing sheet disposed on the diesurface 9 d of the lower die 9 b. Thereafter, as shown in FIGS. 10 and11, air vents 9 e formed in the resin molding die 9 and the throughholes 1 n and trenches 1 h formed in the lead frame 1 are positioned tocorrespond to each other, and clamping of the resin molding die 9 isperformed so that the leads 1 a of the lead frame 1 come into closecontact with the film sheet 8. That is, the die clamping is performed ina state in which the through holes 1 n and trenches 1 h of the leadframe 1 are positioned below the air vents 9 e formed in the upper die 9a of the resin molding die 9.

After the die clamping, the sealing resin 7 is injected into thecavities 9 c of the resin molding die 9 to form a resin flow 10, asshown in FIG. 12, and air present within each cavity 9 c is extrudedinto each air vent 9 e by virtue of an influent pressure of the sealingresin 7. A portion of the air thus extruded into the air vent 9 e flowsat first into the through hole 1 n, and then it flows out from thethrough hole 1 n by virtue of the resin injection pressure exerted onthe air from the trench 1 h. That is, the air which has once entered thethrough hole 1 n is extruded from the through hole 1 n to the exteriorthrough the air vent 9 e and the trench 1 h.

Thus, since air does not stay within the through hole 1 n, it becomeseasier for the sealing resin to get into the through hole 1 n. As aresult, a portion of the sealing resin 7 leaking into the air vent 9 eflows into the through hole 1 n, as shown in FIGS. 13 and 14. In thisway, the sealing resin 7 is filled into the cavity 9 c and the throughhole 1 n.

After the completion of filling of the sealing resin 7, the sealingresin is cured, and, thereafter, the die is released. That is, the lowerdie 9 b and the upper die 9 a are separated from each other. At thistime, according to the semiconductor device manufacturing method of thisembodiment, a portion of the sealing resin 7 leaking into the air vent 9e is fitted into the through hole 1 n in the lead frame 1, and, further,the resin portions flowing out from the air vents 9 e and trenches 1 hjoin (engage each other) in the through hole 1 n, so that the bondingforce between the sealing resin 7 after curing and the lead frame 1 inthe vicinity of the air vent 9 e can be enhanced. Further, the sealingresin 7 leaking into the air vent 9 e is allowed to adhere to and remainon the lead frame 1 side, and, thus, the die can be released in such amanner that the sealing resin 7 scarcely remains within the air vent 9e.

After resin sealing, the leads are cut (division into individual pieces)in step S5, as shown in FIG. 5. In this step, the leads 1 a andsuspending leads 1 e are cut and separated from the frame portions 1 p,that is, the lead frame is divided into individual device regions atpositions slightly outside of a mold line 11, as shown in FIG. 7. As aresult, the QFN is completed in step S6.

According to the semiconductor device manufacturing method of thisembodiment and on the basis of the lead frame used therein, throughholes 1 n are formed outside the suspending leads 1 e in the lead frame1, and trenches 1 h communicating with the through holes 1 n are formedon the back surface side along the suspending leads 1 e, whereby, wheninjecting the sealing resin 7 into the cavities 9 c of the resin moldingdie 9, air which has entered the through holes 1 n by virtue of theinfluent pressure of the sealing resin 7 in the air vents 9 e andtrenches 1 h can be allowed to flow out from the through holes 1 n.

Since air does not stay within the through holes 1 n, it becomes easierfor the sealing resin 7 to enter the through holes 1 n, and the sealingresin 7 leaking to the air vents 9 e can be filled into the throughholes 1 n. As a result, it is possible to enhance the bonding forcebetween the sealing resin 7 after curing and the lead frame 1 in thevicinity of the air vents 9 e. The sealing resin 7 leaking to the airvents 9 e can be allowed to adhere to and remain on the lead frame 1side at the time of release of the resin molding die 9, and it ispossible to effect the die release while allowing little sealing resin 7to remain within the air vents 9 e on the die side.

Consequently, it is possible to prevent clogging of the air vents in theresin molding die 9, and, hence, it is possible to decrease the cleaningfrequency of the resin molding die 9. As a result, it is possible toimprove the throughput in the resin sealing process during assembly ofthe QFN 5.

For example, the cleaning frequency for the resin molding die 9, whichhas so far been once per lot, can be decreased to about once per 600shots. Thus, it is possible to not only make the resin sealing workefficient, but also to greatly improve the throughput in the resinsealing work.

Besides, since it is possible to prevent clogging of the air vents inthe resin molding die 9, it is possible to decrease the occurrence ofnon-filling of the sealing resin 7. As a result, it is possible toimprove the quality of product (QFN 5).

Thus, at the time of cutting the corners for dividing the lead frameinto individual pieces, it is possible to prevent the occurrence ofchipping and cracking of the packages, and, hence, it is possible toimprove the quality of the product (QFN 5).

The following description is directed to modifications of theabove-described embodiment.

In FIG. 15, each of the through holes 1 n formed in the lead frame 1 isformed to have an elongated rectangular shape. Preferably, the throughhole 1 n is formed so that the length in the longitudinal directionthereof is larger than the width of each air vent 9 e in the resinmolding die 9.

As a result, the through hole 1 n can surely be positioned below the airvent 9 e in the upper die 9 a, and, hence, it becomes easier to fill thesealing resin 7 into the through hole 1 n. Consequently, it is possibleto effect die release while enhancing the bonding force between thesealing resin 7 after curing and the lead frame 1 in the vicinity of theair vents 9 e.

From the standpoint that each of the through holes 1 n is to be formedso as to be sufficiently larger (wider) than the width of each air vent9 e, the through hole may be formed in a sufficiently large circularshape. However, since the distance from the gate runner 9 f in thedevice region 1 m adjacent to the through hole 1 n is very short, thesealing resin 7 flows into the air vent 9 e from the adjacent deviceregion 1 m. Therefore, in the case of forming the through hole 1 n tohave an elongated rectangular shape, as shown in FIG. 16, it ispreferable that the through hole 1 n be formed in so as to extend alongthe direction of the gate runner 9 f, which is disposed in the adjacentdevice region 1 m (see FIG. 6) in proximity to the through hole 1 n. Asa result, even in the case where the gate runner 9 f in the adjacentdevice region 1 m is close to the through hole 1 n, the length in thelongitudinal direction of the rectangular through hole 1 n can be madesufficiently larger than the width of the air vent 9 e.

However, by use only of the features of this embodiment (modification),wherein the trench 1 n communicating with the through hole 1 n is notformed, it is impossible to completely remove the air staying within thethrough hole 1 n, and, hence, there is a fear that the sealing resin 7may flow along the upper portion (upper die side) of the air vent 9 e.

Although the through hole 1 n used in this embodiment (modification) isrectangular in shape, the through hole 1 n may be, for example, ellipticin shape so long as it is sufficiently longer than the width of the airvent 9 e and does not come into contact with the gate runner 9 f in theadjacent device region 1 m.

FIG. 17 shows another modification in which a slit 1 q is formed nearthe through hole 1 n in the frame portion 1 p of the lead frame 1, inaddition to the trench 1 h communicating with the through hole 1 n, anda second trench 1 r communicating with both the slit 1 q and the throughhole 1 n is formed.

Thus, since the trench 1 h and the second trench 1 r communicating withthe slit 1 q are formed in the lead frame 1, air which has entered thethrough hole 1 n through the air vent 9 e and trench 1 h can be allowedto flow out from the through hole 1 n through the second trench 1 r,whereby the air present within each cavity 9 c can be removed moreeasily. Moreover, it is easier for the sealing resin 7 to flow in theair vent 9 e, and, hence, it is possible to diminish the formation ofvoids. Consequently, the sealing resin 7 can be surely injected not onlyinto the cavity 9 c, but also into the through hole 1 n.

Like the trench 1 h, the second trench 1 r may be formed by half etchingor stamping.

FIG. 18 shows a further modification wherein a trench 1 h such as shownin FIG. 17 is not formed. A through hole 1 n and a slit 1 q are formedin the frame portion 1 p, and a second trench 1 r which providescommunication between the through hole 1 n and the slit 1 q is formed.In this case, air which has entered the through hole 1 n is extrudedtoward only the slit 1 q through the second trench 1 r, whereby thesealing resin 7 can be injected sufficiently into the through hole 1 n.

Although, in the above-described embodiments, the trenches 1 h areformed on the back surface side opposite to the chip mounting side ofthe lead frame 1, the trenches 1 h may be formed on the chip mountingside, or they may be formed on both the front surface (the chip mountingside) and the back surface (the side opposite to the chip mountingside). Forming the trenches on both the front surface and the backsurface can be effected by forming them in positions which are deviatedfrom each other to avoid overlapping.

Although the present invention has been described above on the basis ofembodiments thereof, it goes without saying that the invention is notlimited to the above-described embodiments, but that various changes maybe made within a scope not departing from the gist of the invention.

For example, in the above-described embodiments, although reference hasbeen made to a QFN 5 as an example of the semiconductor device, thesemiconductor device may be of a type other than a QFN so long as it isassembled by using the lead frame 1 and by resin molding with use of aresin molding die.

In the above-described embodiments, although the injection of resinduring resin molding is performed while covering the individual deviceregions 1 m of the lead frame 1 with individual cavities 9 c of a resinmolding die 9, the injection of resin may be carried out in a state inwhich plural device regions 1 m are covered all together with one cavity9 c.

The resin molding process adopted in the semiconductor devicemanufacturing method according to the above embodiments is alsoapplicable to a case where a sealing sheet, such as the film sheet 8, isnot used.

The present invention is suitable for use as a semiconductor devicemanufacturing technique.

1. A method of manufacturing a semiconductor device, comprising thesteps of: (a) providing a lead frame, the lead frame having chipmounting portions, suspending leads connected to the chip mountingportions, a plurality of leads arranged around each of the chip mountingportions, through holes formed outside the suspending leads in extendingdirections of the suspending leads, and first trenches formed along thesuspending leads on a back surface side opposite to the chip mountingportion side so as to communicate with the through holes; (b) mountingsemiconductor chips respectively over the chip mounting portions; (c)connecting electrodes of the semiconductor chips and the leads with eachother through electrically conductive wires; (d) disposing the leadframe over a die surface of a resin molding die, thereafter making airvents formed in the resin molding die and the through holes and thefirst trenches formed in the lead frame correspond to each other,clamping the resin molding die, then injecting sealing resin intocavities of the resin molding die, allowing air which has entered thethrough holes to flow out of the through holes by virtue of an influentpressure of the sealing resin from the air vents and the first trenches,and performing resin sealing so that the sealing resin is injected intothe cavities and the through holes; (e) after the resin sealing,allowing the sealing resin to remain in the through holes of the leadframe and releasing the resin molding die; and (f) separating the leadsand the suspending leads from the lead frame to divide the lead frameinto the individual chip mounting portions.
 2. The method according toclaim 1, wherein the through holes of the lead frame are formed so as tobe located outside the cavities and in positions corresponding to theair vents during clamping of the resin molding die.
 3. The methodaccording to claim 1, wherein the lead frame is plated with palladium.4. The method according to claim 1, wherein the resin sealing step (d)is carried out by injecting the sealing resin into the cavities in astate in which individual device regions over the lead frame are coveredwith the individual cavities respectively.
 5. The method according toclaim 1, wherein, in the resin sealing step (d), the lead frame isdisposed over a sealing sheet placed over the die surface of the resinmolding die, then the resin molding die is clamped in such a manner thatthe leads of the lead frame come into close contact with the sealingsheet, and thereafter the sealing resin is injected into the cavities ofthe resin molding die.
 6. The method according to claim 1, wherein thelead frame includes slits formed around the leads and second trencheswhich provide communication between the slits and the through holes, andin the step (d), the sealing resin is injected into the cavities of theresin molding die, air which has entered the through holes is allowed toflow out of the through holes via the second trenches by virtue of aninfluent pressure of the sealing resin from the air vents and the firsttrenches, and resin sealing is performed so that the sealing resin isinjected into the cavities and the through holes.
 7. A method ofmanufacturing a semiconductor device, comprising the steps of: (a)providing a lead frame, the lead frame having chip mounting portions,suspending leads connected to the chip mounting portions, a plurality ofleads arranged around each of the chip mounting portions, through holesformed outside the suspending leads in extending directions of thesuspending leads, and trenches formed along the suspending leads on thesame side as the chip mounting portion side so as to communicate withthe through holes; (b) mounting semiconductor chips respectively overthe chip mounting portions; (c) connecting electrodes of thesemiconductor chips and the leads with each other through electricallyconductive wires; (d) disposing the lead frame over a die surface of aresin molding die, thereafter making air vents formed in the resinmolding die and the through holes and trenches formed in the lead framecorrespond to each other, clamping the resin molding die, then injectingsealing resin into cavities of the resin molding die, allowing air whichhas entered the through holes to flow out of the through holes by virtueof an influent pressure of the sealing resin from the air vents and thetrenches, and performing resin sealing so that the sealing resin isinjected into the cavities and the through holes; (e) after the resinsealing, allowing the sealing resin to remain in the through holes ofthe lead frame and releasing the resin molding die; and (f) separatingthe leads and the suspending leads from the lead frame to divide thelead frame into the individual chip mounting portions.
 8. The methodaccording to claim 7, wherein the through holes of the lead frame areformed so as to be located outside the cavities and in positionscorresponding to the air vents during clamping of the resin molding die.9. The method according to claim 7, wherein, in the resin sealing step(d), the lead frame is disposed over a sealing sheet placed over the diesurface of the resin molding die, then the resin molding die is clampedin such a manner that the leads of the lead frame come into closecontact with the sealing sheet, and thereafter the sealing resin isinjected into the cavities of the resin molding die.
 10. A method ofmanufacturing a semiconductor device, comprising the steps of: (a)providing a lead frame, the lead frame having chip mounting portions,suspending leads connected to the chip mounting portions, a plurality ofleads arranged around each of the chip mounting portions, through holesformed outside the suspending leads in extending directions of thesuspending leads, and trenches formed in both a surface and a backsurface of the lead frame along the suspending leads and at deviatedpositions to avoid overlapping each other and so as to communicate withthe through holes; (b) mounting semiconductor chips respectively overthe chip mounting portions; (c) connecting electrodes of thesemiconductor chips and the leads with each other through electricallyconductive wires; (d) disposing the lead frame over a die surface of aresin molding die, thereafter making air vents formed in the resinmolding die and the through holes and trenches formed in the lead framecorrespond to each other, clamping the resin molding die, then injectingsealing resin into cavities of the resin molding die, allowing air whichhas entered the through holes to flow out of the through holes by virtueof an influent pressure of the sealing resin from the air vents and thetrenches, and performing resin sealing so that the sealing resin isinjected into the cavities and the through holes; (e) after the resinsealing, allowing the sealing resin to remain in the through holes ofthe lead frame and releasing the resin molding die; and (f) separatingthe leads and the suspending leads from the lead frame to divide thelead frame into the individual chip mounting portions.
 11. The methodaccording to claim 10, wherein the resin sealing step (d) is carried outby injecting the sealing resin into the cavities in a state in whichindividual device regions over the lead frame are covered with theindividual cavities respectively.
 12. The method according to claim 10,wherein, in the resin sealing step (d), the lead frame is disposed overa sealing sheet placed over the die surface of the resin molding die,then the resin molding die is clamped in such a manner that the leads ofthe lead frame come into close contact with the sealing sheet, andthereafter the sealing resin is injected into the cavities of the resinmolding die.
 13. A method of manufacturing a semiconductor device,comprising the steps of: (a) providing a lead frame, the lead framehaving a plurality of device regions, the device regions each includinga chip mounting portion, suspending leads connected to the chip mountingportion, and a plurality of leads arranged around the chip mountingportion, the lead frame further having through holes formed outside thesuspending leads in extending directions of the suspending leads andeach disposed in an elongated shape along an extending direction of agate runner in a device region adjacent thereto; (b) mountingsemiconductor chips respectively over the chip mounting portions in thedevice regions; (c) connecting electrodes of the semiconductor chips andthe leads with each other through electrically conductive wires; (d)disposing the lead frame over a die surface of a resin molding die,thereafter making air vents formed in the resin molding die and thethrough holes formed in the lead frame correspond to each other,clamping the resin molding die, then injecting sealing resin intocavities of the resin molding die through respective gate runners,allowing air which has entered the through holes to flow out of thethrough holes by virtue of an influent pressure of the sealing resin,and performing resin sealing so that the sealing resin is injected intothe cavities and the through holes; (e) after the resin sealing,allowing the sealing resin to remain in the through holes of the leadframe and releasing the resin molding die; and (f) separating the leadsand the suspending leads from the lead frame to divide the lead frameinto the individual device regions.